Quoted from "mrfixit" I don't have a clue what I'm looking at there. K-Rain has a solenoid like that. Maybe you can find a model number or name on the valve. That's a pretty distinctive solenoid. Good to know.

Quoted from "Eric1116" https://www.instagram.com/p/Bltt6wXFaze/?utm_source=ig_web_copy_link You are probably looking at Zinc Oxide. The temperatures for casting brass are fairly close to the melting point of zinc, so a bit of zinc might migrate to the surface of the cast part, where it can later oxidize. Do not worry about it. And do not paint the backflow preventer.

Quoted from "DallasJW" It would benefit everyone, if uninformed amateurs would step back from their prideful ignorance, when it comes to commenting on matters of public safety there are plumbing codes for a reason there are backflow preventers for a reason there are different types of backflows with varying risks people have been sickened and killed by what was in the water that "ran the wrong way" in pipes

For your application, the backflow preventer must be an RPZ, and it's just too bad that they cost hundreds of dollars. Save your money and buy some hose-end sprinklers, if you must have watering beyond your allotment. Much more simple and economical.

Pro-HC - Factory Reset From the home screen please tap on Settings. Next tap on Config. Tap on Factory Default. Finally, tap on Erase Config. Congratulations, you have now successfully factory reset your controller and is now ready for fresh configuration settings, manually or automatically by synchronising it with your Hydrawise account.

Quoted from "DallasJW" I have seen people simply put a loop in some garden hose and use that as a backflow preventer. The simple fact that you even realize that this is something to consider puts you ahead.. In my amateur, uneducated opinion, as long as you don't have any steep grades and pipe the system above the highest head at the spigot, maybe with a loop, you're fine. Someone who is ranting about the backflow preventers explain to me how water at almost atmospheric pressure would flow back...

Quoted from "mrfixit" I'd put a sprinkler at 2:30 pm of that top arc. I see a brown spot happening there. Where there is only single coverage from the smaller full circle head? I'd lose that full circle in favor of a half-circle on the border, completing a head-to-head layout on the back border, and maybe alter the half circle next to the "future driveway" into two part circle heads next to each other, with their total arcs making for the same half-circle arc of the replaced head, and with one ...

Consider replacing all the old W*M diaphragms, which will reset the clock on a key system component. And yes, the diaphragm was next in the chain of diagnostics. A pro would have known by the look and feel of the old one that it was time for a new one, but that look and feel does not translate into words, hence the solenoid and exhaust port test.

There is no irrigation backflow preventer showing in your photo. There is showing a "Dual Check Valve" device, which is a just-in-case device commonly seen installed just downstream of water meters. It has no value as proven protection. It is only a backup device. Primary protection cames from either a Pressure Vacuum Breaker or a Reduced Pressure Zone device, those commonly known by the acronyms PVB and RPZ

Rotor heads with 3/4-inch connections are going to be more durable. The only popup rotors with 1/2-inch connections that are likely to become commonplace are the MP Rotator types, which would fit your application, given the shorter spray distances you have.

You don't need a 100 mesh filter on city water supplies. As for valves, don't drift too far away from valves you can easily get replacement parts for. All valves will eventually need servicing, so don't make it hard on yourself.